This application is based on and incorporates herein by reference Japanese Patent Applications No. 2000-337842 filed on Nov. 6, 2000 and No. 2001-161893 filed on May 30, 2001.
The present invention relates to an alternator such as a brushless-type alternator for vehicles such as passenger cars and trucks, and a method of manufacturing the same.
In brushless-type alternators (alternating current generators), a field coil is wound on a field core, which is provided separately from a rotor core and fixed to a frame so that only the rotor core rotates in the electric power generating operation. For rotation in the power generating operation, the rotor core is spaced apart from the field core with a clearance from the field core. This clearance causes magnetic loss and reduced electric power generated by the alternator when compared with a normal brush-type alternator of the similar size.
JP-A-4-165950 and JP-A-4-251553 teach brushless-type alternators, which have permanent magnets between adjacent nails of a rotor core to restrict leakage flux occurring between the nails. The nails and the permanent magnets are integrated with a holding member to restricting the permanent magnets from dropping off from the rotor core. However, this arrangement results in complicated constructions around the permanent magnets and complicated manufacturing and assembling processes.
The present invention addresses this problem, and has an object to improve electric power generated by an alternator without complicating manufacturing and assembling processes.
According to the present invention, an alternator has a rotor, which comprises a pair of pole cores. The pole cores include a plurality of nail parts arranged alternately in a rotating direction, respectively. The nail parts are coupled to each other with a non-magnetic ring. A permanent magnet is interposed between adjacent two of the nail parts, and fixedly held in position with the non-magnetic ring. The permanent magnets are located radially inside or outside the non-magnetic ring.